This study will examine the social context and hormonal control of an electrocommunicatory behavior in female Apteronotus leptorhynchus, a weakly electric fish. The project will study how testosterone (T) affects behaviors at the level of pacemaker nucleus of the brain where neural control of the behavior lies. The communication signal studied is sexually dimorphic and the basis of this differentiation is unknown. It is hypothesized that T modulates female behavior and the effects are mediated via glutamate receptors in the pacemaker nucleus. The hypothesized social function of the behavior as a communication signal to males and/or females will also be tested. This study will contribute to the understanding of how hormonal effects on behavior are mediated, and how male and female nervous system may differ in vertebrates.